The present invention relates to a press-fit electrical connector pin having a compliant portion for press-fit connection to a plated-through hole in a printed circuit board.
Terminal pins with compliant sections or portions (sometimes called press-fit pins) have been known in the art for many years. Compliant pins are designed to be inserted into a plated-through hole in a printed circuit board or other conductive plate.
The pin generally includes a mating portion adapted to contact an electrically conductive element and a compliant portion extending from the mating portion and adapted to make electrical contact with conductive material defining the interior surface of the plated-through hole. The compliant portion is generally configured with one or more hinge areas that bend or flex as the pin is inserted in the hole, allowing the pin to compress to fit into the hole. The pin is thereby retained within the hole by frictional engagement between the pin and the hole walls, creating a solder-free electrical connection between the pin and the conductive interior surface of the hole.
One type of press-fit pin, as shown in U.S. Pat. No. 4,464,009 FIG. 6, has a compliant portion with a cross section configured in the shape of an xe2x80x9cM.xe2x80x9d A pair of substantially parallel elastically deformable beam members makes up the outside leg portions and a xe2x80x9cVxe2x80x9d-shaped cross member interconnects the beams therebetween. The xe2x80x9cVxe2x80x9d-shaped cross member of the xe2x80x9cMxe2x80x9d configuration allows the press-fit section of the pin to resiliently deform when the pin is inserted into the board hole. The xe2x80x9cVxe2x80x9d-shaped cross member also allows the pin to accommodate variances in hole diameter while maintaining a low insertion force.
Such a pin can be stamped from sheet metal using a punch-die combination. Typically, the die has a female recess with a xe2x80x9cVxe2x80x9d-shaped angular area, the punch having similar configurations. Because of the acute angles in xe2x80x9cVxe2x80x9d-shaped areas, this type of punch-die is more susceptible to damage and wear and consequently is expensive to maintain.
The xe2x80x9cVxe2x80x9d-shaped cross member gives the press-fit portion flexibility which allows the pin to accommodate variations in the printed circuit board hole diameter. A slight variation in the metal thickness of the xe2x80x9cVxe2x80x9d-shaped member can affect the flexibility of the press-fit portion which can affect the frictional engagement forces between the pin and the hole walls. Consequently, variations in the mechanical characteristics of the pin can affect electrical performance. Therefore, it is desirable during manufacturing that the metal thickness of the xe2x80x9cVxe2x80x9d-shaped member is held constant. The xe2x80x9cVxe2x80x9d shape, however, makes it difficult to measure the exact thickness of the metal at this critical location. It would be desirable to provide a press-fit pin with consistent mechanical characteristics that is easy to manufacture.
The present invention provides an elongated connector pin, fabricated of electrically conductive material and adapted to be press-fitted into a plated-through hole of a printed circuit board to make a solder-free electrical connection, with consistent mechanical characteristics that is easily manufactured. To attain these objects the press-fit portion of the present invention has a cross section which has a flat section in its beam-to-beam cross member, thereby eliminating the necessity of forming acute angular areas in the dies and punches.
More specifically, the press-fit pin of the present invention has an elastically deformable area to be inserted into a plated through hole in a printed circuit board. The elastically deformable area comprises two opposite, parallel beam regions connected by a connecting deformable bridge. The outer corners of each beam region engage the inner wall of the plated through hole while permitting said connecting deformable bridge to be deformed. The present invention is an improvement in that the cross-section of the elastically deformable area includes a deformable bridge with a flat section extending perpendicular to said parallel-beam regions, and two oblique sections extending outward from the opposite ends of the upper surface of said flat section to be contiguous with said parallel beam regions. The flat section of the bridge replaces the xe2x80x9cVxe2x80x9d-shaped area of the conventional press-fit pin, thus eliminating acute angles in the die-and-punch and facilitating measurement of metal thicknesses at the flat section.
The connecting deformable bridge may have, on the under-side (or lower surface), a reentrant section formed at each corner transferring from each end of the connecting flat section to the inner rising wall of each beam region. The particular reentrant shape of transfer corner eliminates all acute angles from the press-fit pin.
The press-fit pin of the present invention is further improved in that the upper flat surface of the connecting deformable bridge is located at an intermediate level of the bean height. The positioning of the upper flat surface 10a at the intermediate level of the beam height allows the four outer corners 8a of the opposite beams 8 to apply same contact pressures to the inner wall of the plated through hole. The flatness of the bridge facilitates the measuring of its thickness, thereby permitting production of press-fit pins of one and same shape by lots, and hence one and same physical characteristics by lots.
Other objects and advantages of the present invention will be understood from the following description of a press-fitting pin according to a preferred embodiment of the present invention: